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FreeBSD-EN-20:13.bhyve                                          Errata Notice
                                                          The FreeBSD Project

Topic:          Host crash in bhyve with PCI device passthrough

Category:       core
Module:         bhyve
Announced:      2020-07-08
Credits:        Peter Grehan
Affects:        FreeBSD 12.1
Corrected:      2020-06-01 05:14:01 UTC (stable/12, 12.1-STABLE)
                2020-07-08 19:56:34 UTC (releng/12.1, 12.1-RELEASE-p7)

For general information regarding FreeBSD Errata Notices and Security
Advisories, including descriptions of the fields above, security
branches, and the following sections, please visit
<URL:https://security.FreeBSD.org/>.

I.   Background

bhyve(8) is a hypervisor that supports running a variety of guest operating
systems in virtual machines.  bhyve(8) includes support for PCI devices
passthrough (a technique to pass host PCI devices to a virtual machine for its
exclusive control and use).

II.  Problem Description

When an attempt is made to pass through a PCI device to a bhyve(8) VM (causing
initialization of IOMMU) on certain Intel chipsets using VT-d the PCI bus
stops working entirely resulting in a host crash.  This issue occurs at least
on the Intel Skylake series processors and those released later.

A device passed through to a guest VM running OpenBSD at least since version
6.4 on both AMD and Intel processors may not fully work in the guest.  OpenBSD
issues 4-byte PCI configuration-space register reads and writes to consecutive
2-byte fields, which were not handled correctly by bhyve(8).

III. Impact

These issues prevent using bhyve in production with some combinations of host
hardware and/or guest operating system.

IV.  Workaround

No workaround is available.  Systems not using bhyve(8) for virtualization
with PCI passthrough are not affected.

V.   Solution

Upgrade your system to a supported FreeBSD stable or release / security
branch (releng) dated after the correction date and reboot.

Perform one of the following:

1) To update your system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install
# shutdown -r +10min "Rebooting for errata update"

The first problem requires a reboot as the affected part is the kernel.

The second problem does not require a reboot as the affected part is the
bhyve userland executable.

2) To update your system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch https://security.FreeBSD.org/patches/EN-20:13/bhyve.patch
# fetch https://security.FreeBSD.org/patches/EN-20:13/bhyve.patch.asc
# gpg --verify bhyve.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile the operating system using buildworld and installworld as
described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

d) Recompile your kernel as described in
<URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/12/                                                        r361686
releng/12.1/                                                      r363022
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=229852>

<URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=245392>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-20:13.bhyve.asc>
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